Smoothed Boundary Method Simulations of Complex Electrode Microstructures Using Adaptive Mesh

Abstract

Rechargeable battery electrodes comprise of highly complex microstructures and convoluted electrolyte courses. These configurations dictate the macrohomogeneous properties and electrochemical performances of the electrodes. In addition to the geometric complexity, multiple concurrent physical mechanisms take place in the electrochemical processes of charge-discharge cycles. Understanding these detailed processes occurring in the complex electrode microstructure is the key to improve the design of electrodes. In this work, we present a framework to implement detailed electrochemical simulations in complex electrode microstructures. The framework employs the Smoothed Boundary Method(SBM)[1] which allows simple and fast mesh generation for complex geometries. In SBM, a continuous domain parameter is utilized to distinguish the phases of electrode particles and electrolyte, wherein the particle-electrolyte interface is defined by the region where the domain parameter transitions from zero to one in a continuous manner. With the electrochemical governing equations reformulated using the domain parameter, conformal mesh to the complex geometries is circumvented in the simulations. The SBM is implemented with Octree-based adaptive mesh refinement (AMR)[2], in which fine cubic meshes are generated near the particle-electrolyte interfaces while coarse cubic meshes are used in the bulk regions of particles and electrolyte. As a result, the diffuse interface in the SBM is effectively decreased and the accuracy of the electrochemical simulations is comparable to those of conventional sharp-interface methods. Intercalation electrode materials, namely NMC for the cathode and graphite for the anode, are used in the simulations to reveal the detailed electrochemical processes in the complex electrode microstructures and as a demonstration of the presented simulation framework. Material parameters in the simulations are directly obtained from experimental data to study the electrochemical phenomena occurring in the microstructures. The results can be used to extract macrohomogeneous electrode properties in the Porous Electrode Modeling for device-level simulations. Thus, it is shown that the presented simulation framework can serve as a useful tool for examining the effects of electrode microstructures and intrinsic material properties on the electrodes’ performance and as well as for electrode design.